What precautions should I take? Is it just a matter of wrapping the structure in poly? What is the best way to vent? How do I seal the seams?

I am planning to use 5 mil poly for the top and sides, but I am in Connecticut and will have to keep it heated during the cold months. Is there a different material that I should consider that may insulate a little better?

So many questions... Not sure where to start. Any advice or guidence is greatly appreciated.

Good points TCLynx. The box just lists the frame as "heavy gauge steel". It does have some good weight to it, but that is not neccrssarily a determining factor for strength - additional structural support sounds like a wise choice.
Yikes! I didn't even think about long term effects of UV.

TCLynx said:

Will a canopy be able to handle the snow load?

If you go with just poly, be sure you get stuff that will survive more than a few months under UV. Actual greenhouse film will do better than just getting builders plastic.

You will need to do some sort of frame on the ends to support a door and be able to have vented windows.

Perhaps you could figure out some way to do a double layer with an inflation fan for more insulation?

Check out Eliot Colemans book The Winter Harvest Handbook. I built a 12'x 30'x 7' hoophouse using the plans from http://www.johnnyseeds.com/c-700-quick-hoops-high-tunnels.aspx. I erected in Colorado and it handle the snow loads excellently. I am erecting it here now in Lincoln,NE and it should do as well. The greenhouse film, hoopbender and fittings can be had on the Johnnys site as well. I used low tunnels inside it as well and grew cold weather crops through the winter. I also had an AP system in there with goldfish that worked great. One note I did not add supplemental heat. Good luck buddy:)

You might be able to do some minor modifications to your canopy to perhaps keep snow from collecting on the top. Maybe come arches between the peak to the sides that could keep the top curved instead of letting them sag in.

Wow! Thanks all. This is just what I needed. Tons of great info (and possibilities). I have quite a bit of homework to do. I am sure I'll have more questions along the way and will keep you posted with my progress.

I used a similar frame, one from a portable garage set up. I added extra ribs to mine, making them less than 2 feet apart. I used 1/2" steel conduit and a conduit bender to make the bends. I laid the extra ribs over the main ridge support and zip tied them in place. I also zip tied the vertical portions to the side rails and attached them to a 2x4 that I ran around the bottom, with a conduit clamp. As for the ends, I framed it in with 2x4's to make the door frame. The opposite end I just used 1x3's.

The plastic, I just draped over the frame, from one side, up over the top, then down to the bottom on the other side. To attach all this to the frame, I used what are called TEK screws, they are just self tapping sheet metal screws. The plastic is held in place with lath strips attached with the TEK screws also. So far, this has held up to 45 mph wind, we will see how the winter goes.